Transmission



Oct. 10, 1944. G. A. WAHLMARK 2,360,025

TRANSMISS ION Filed June 5, 1941 10 Sheets-Sheet l INVENT OR.

1944- G. A. WAHLMARK TRANSMISSION '10 Sheets-Sheet 2 Filed June 5, 194

Oct. 10, 1944. G. A. WAHLMARK TRANSMISS ION Filed June 5, 1941 10 Sheets-Sheet 5 MMN INVE OR.

Oct. 10, 1 944. WAHLMARK 2,360,025

TRANSMISS ION Filed June 5, 1941 10 Sheets-Sheet 4 Oct. m, 1944. G. A. WAHLMARK TRANSMIS S ION l0 Sheets-Sheet 5 Filed June 5, 1941 whww I N VEN TOR. Gwzzzar @Zfla/wmr/Z Oct. m, 1944. G. A. WAHLMARK ,3

TRANSMISSION Filed June 5, 1941. 10 Sheets-Sheet 6 5202220)" QJZZWZO/WQ @cfio w, 19 a. A. WAHLMARK 3 9 TRANSMISSION Filed June 5, 1941 10 Sheets-Sheet 8 llllllll l Efi-i IN VENTOR.

Oct. 10, 1944. e. A. WAHLMARK TRANSMISSION Filed June 5, 1941 10 Sheets-Sheet 9 bNN Oct. 10, 1944. WAHLMARK 2,360,025

TRANSMISSION Filed June 5, 1941 10 Sheets-Sheet 1O 1N VENTOR. BY GzuzrzarQ lfla/zZmar b,

and @e L;

Patented Oct. 10,

UNITED STATES PATENT OFFICE TRANSMISSION. Gunnar A. Wahlmark, Rockford, Ill. Application June 5, 1941, Serial No. 396,646

28 Claims.

This invention relates to transmissions and more particularly to a fluid operated transmission for usein an automotive vehicle. It is the general object of the invention to provide a new and improved transmission of this type.

Another object of the invention is to provide a new and improved fluid transmission which is compact, efllcient in operation, and which provides for smooth and stepless automatic acceleration.

Another object is to provide a fluid transmission operable automatically to provide maximum safe acceleration at all times.

Another object is to provide a new and improved fluid transmission operable to"multiply the torque available at the driven shaft with substantially no limit .tion to the ratio and more particularly to provide such a transmission wherein the torque multiplication may be as high as 1000:1.

Another object is to provide a fluid transmission embodying pump and motor devices of the Wobbler type and more particularly to provide such a transmission wherein substantially con-- stant pressure is maintained on the wobblers al' though the working pressure of the pistons varies.

Another object is to provide an automatic fluid transmission embodying a pump together with torque controlled means for governing the displacement of the pump.

Another object is to provide a fluid transmission embodying a pump and motor and means operable automatically to eifect a direct drive wherein the pump and motor rotate as a unit with their shafts.

Another object is to provide a fluid transmission having readily adjustable means for varying, under similar conditions of operation, the rate of acceleration of the vehicle with which the transmission is associated.

Another object is to provide a fluid transmission embodying a pump and a motor housed in the same rotatably mounted casing, a brake for holding the casing against rotation under the reaction torque, and means responsive to thereaction torque controlling the brake.

Another object is to provide a fluid transmission embodying a pump, a motor, and control means, and means for supplying make-up and control fluid, .the fluid supply means being arranged to assure the supply of make-up fluid prior to the supply of control fluid.

Another object is to provide a fluid transmission manually conditionable while in neutral or at idling in. forward, to provide a hill-holding."

.eflect on thevehicle in which the transmission is incorporated.

Further objects will become readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a longitudinal central section a preferred form of the invention.

Fig. 1 is a fragmentary section along the line I of Fig. 1.

Fig. 1 is a fragmentary I of Fig. 1.

Fig. 2 is a section approximately along the line 2-2 of Fig. 1.

Fig. 3 is a section takn approximately at right angles to the section of Fig. 1 (line 3-3 of Fig. 1) and showing part of the structure at the left end of Fig. 1.

Fig. 4 is a section approximately along the line 4-4 of Fig. 1.

Fig. 5 is a section approximately along the line 55 of Fig. 3.

Fig. 6 is an elevational view looking at the left hand end of Fig. 1 and partly in section along the line 6-8 of Fig. 7.

Fig. '7 is a fragmentary view partly in section along the line l-i of Fig. 6.

through section along the line Fig. 8 is a fragmentary section along the line 9-8 of Fig, '7.

Fig. 9 is a fragmentary elevational view along the line 99 of Fig. 6.

Fig. 10 is a section along the line ill-l0 of Fig. 9.

Fig. 10 is a section along the line Hl-l0 of Figs. 6 and 10.

Fig. 11 is a fluid circuit diagram.

Fig. 12 is an enlarged sectional view approximately along the line l2|2 of Fig. 1 and rotated Fig. 13 is a still further enlarged fragm'entary section through a modified form of automatic .valve, approximately along the line [3-43 of Fig. 14.

Fig. 14 is a similarly enlarged fragmentary section along the line H-l 4 of Fig. 13.

Fig. 15 is a fluid circuit diagram of the modifled form of the invention with the manual control valve in its neutral position. I

Fig. 15 is an enlarged fragmentary view of the centrifugal valve means, better to show the valve in the position which it has in Fig. 15.

Fig. 16 is a similar fluid circuit diagram with the manual control valve in its'forward position and the transmission functioning to multiply the torque.

. plurality of bolts 22.

2 s I t l lasso,

- Fig. l6 an enlarged fragmentary view of valve in the position which it has in Fig, 17.

- Fig. 18 is a similar fluid circuit diagram with the manual control valve in its reverse position.

Fig. 18' is an enlarged fragmentary view of the centrifugal valve means, better to show the valve in the position which it has in Fig, 18;

Fig. 19 is a fragmentary and enlarged view of one-half of the wobble plate showing the curvature of the contact portion of the wobble plate and the ends of the pistons, and the point of contact for various positions of the pistons.

Fig. 20 is a force diagram showing the point of engagement of the pistons and the effective wobbler arms with the wobbler disposed at a 24 angle.

' Fig. 21 is a force diagram similar to Fig. 20, but with the wobbler disposed at a 6 angle.

While there is illustrated in the drawings and hereinafter described in detail apreferred form of the invention, together with a modification thereof, it is to be understood that I do not intend to limit the invention to the particular forms and various changes may be made by those skilled in the art without departing from the spirit and scope of the invention as expressed in the appended claims.

In the form illustrated in Figs. 1 to 12, the invention includes a somewhat tubular housing having an end plate or closure 2! secured to the right hand end thereof (Fig. 1) by means of a The left hand end of the casing is provided with an end wall 23 having a bore 24. Generally, an adjustable wobbler type pump P occupies the left hand portion of the housing and a flxed wobbler type motor M occupies the right hand portion. Rotatably mountedin the housing 20 is a casing, designated generally 25, said casing having a cup-shaped member 26, a pump cylinder block 21, a valve block 28, a motor cylinder block 29, an annular supporting member 30 at its right hand end, and an annular supporting member 3! at its left hand end. The annular supporting member ii is rptatably mounted on a roller bearing 32, the outer race 33 of which is positioned in the bore 24. The supporting member 30 is rotatably mounted on the end plate 2| by means of a ball bearing 34. Preferably, the parts of the casing 25 are bolted together, the cup-shaped member 26 being bolted to the supporting member 2| by a plurality of set screws 35 arranged in annularly spaced relation, the cup-shaped member 28 being secured to the pump cylinder block 21 by a plurality of bolts 38,

the valve block 28 being secured to the pump and motor cylinder blocks by means of a plurality of bolts 31 and the motor cylinder block'29 being secured to the supporting member 30 by means of a plurality of set screws 38. Although mounted rotatably upon and within the housing 20, the casing is arranged to be held against rotation as hereinafter more fully described by means including a brake band 40 operable against the exterior cylindrical surfaces of the valve block 28 and motor cylinder block 2 9.

The pump P has a shaft which is rotatably mounted on the supporting member 3| by means of a sleeve bearing II and on the pump cylinder block 21 by means of a ball bearing 41. The shaft ll carries a sleeve-like member ll which is provided with a-flange 40 between which and the supporting member Ii are mounted roller bearings l0 and Ii. v

The pump has a plurality of annularly spaced cylinder bores $2 in the cylinder block 21 in which hollow pistons II are reciprocably mounted. As' illustrated herein (Figs. -1 and 2) ,1 the member being rotatably mounted on the inner member by means of a ball bearing 51 and a roller thrust bearing 58. The outer member I! has a curved surface 59 engageable against the adjacent curved end surfaces '0 of the pistons 53. The inner member II (Figs. 1 and 3) is pivotally mounted on the shaft l! by means of a diametrically extending pin 6| which is anchored to the shaft by means of a set screw '2 and at its opposite ends carries needle bearings 83 (Fig. 3) which arepositioned within diametrically opposite bores 64 or the member II.

The wobbler is arranged to be adjusted angularly with respect to the pin OI by means of a piston and cylinder device housed within a recess Bl in the cylinder block 21 As illustrated'herein, this device consists of a piston 86 secured to the shaft 45 and against longitudinal movement-thereon by means of a lock ring 61. The;

ring 81 for holding the piston in place on the shaft is'flrst located in the piston in an expanded condition so that it can slide over the shaft. Three set screws are then used for contracting the snap ring into the groove in the shaft in which position it holds the, piston against longitudinal movement on the shaft. A shiftable cylinder cooperates with the piston "and is -connected to the wobbler by means of an arm 69 which projects from one end wall 10 of the cylinder and has a spherically formed outer end ll engaged in a radially extending bore I2 in the member 55. The cylinder I8 is slidable longitudinally of the shaft and piston. As illustrated in Fig. l, the shiftable cylinder 68 is slidable on bushings I3 and 18 which bushings in turn are slidable on the shaft. Sleeve bushing I3 slidably engages a bore I4 in the end wall 10 and sleeve bushing II slidably engages in a bore in the opposite end wall of the cylinder. The bushings cooperate with the cylinder to determine the neutral position of the wobbler. For

I example, if fluid under pressure is admitted to both ends of the cylinder 68, the cylinder and the bushing 15 will move toward the right from the position in. Fig. 1 until the bushing 15 engages the stop formed by the inner race of the ball bearing 41. The wobbler will then be in its neutral position and the cylinder wall III will engage a flange 16 on the bushing I3. Since the fluid pressure in both ends of the cylinder 88 is then equal, it will act against surfaces of equal size on the cylinder and bushings and hold the wobbler in its neutral .position. The end of the sleeve-like member' acts to limit the movement of the shiftable cylinder toward the left (high speed forward), the movement of the shiftablecylinder toward the right (reverse) being limited by engagement of a counter-balancing and stop portion "a on the wobbler 55 with the sleeve 48.

The invention contemplates the provision of control means for automatically shifting the Wobbler to adjust the stroke of the pistons. Such a means will be described more fully hereinafter.

The cylinders 52.0! the pmnp are provided with cylinder ports 80 (Figs. 1 and 2) which extend through to the end surface of the cylinder block 21 where they comrmmicate with a cylindrical valve chamber II in the valve block 23. The flow of fluid through the cylinder ports 80 is arranged to be by means of a wheel-like valve of the type disclosed and claimed in Letters Patent No. 2,190,812 which issued to me on February 20, 1940. Generally. this valve has a rim 82 and an annular hub 83 connected by a plurality of makes 84- The hub on the valve is mounted by means of a roller bearing 85 on an eccentric 85 (Figs. 1 and 1a.), which eccentric is formed integrally with a sleeve 81 secured to the right handendoftheshaftli by means of a key 08 and in between the adjacent inner race of the ball bearing 41 and a clamping nut 89 secured to the end of the shaft 45. The rim 82 of the valve operatm to connect the cylinder ports 80 alternately with the outer portion of valve chamber II (which connects with a plurality of pump ports 90in the valve block 28) and the inner portion a: the valve chamber which connects with a plurality of pump ports SI formed in the valve block 28. The pump ports 90 and SI communicate with the valve chamber of the motor M as hereinafter more fully described.

As illustrated herein the motor M has a shaft I- Adjacent its inner end this shaft carries a bushing Ill which cooperates with a radial roller bearing I02 and a thrust roller hearing I 03 to support the shaft Ill rotatably on the motor cylinder block 29. The motor has a plurality of cylinder bores I04 spaced annularly about the shaft I00, in which pistons I05 are reciprocably mounted. The cylinders extend through the cylinder block 23 and into the valve block 28. As illustrated herein, the motor has seventeen such cylinders and pistons. These pistons are effective to rotate the shaft I00 through motion converting means of a flxed angle wobble plate having an inner annular member I06 secured to a flange III on the shaft III by means of a plurality of bolts I08, and an outer annular member I08 which is provided with a flat surface IIO arranged to engage the adjacent conically surfaced ends III of the pistons I05. The outer member I09 is rotatably mounted on the inner member I88 by means of a ball bearing H2 and a roller thrust bearing H3. The inner member I06 is miatably supported with respect to the casing supporting member 30 by means of a bushing III (secured to the member 30 by a plurality of bolts 5), a. roller bearing H6 and a. roller thrust bearing "'0. Preferably, an oil seal H8 is positioned between-the shaft I00 and the end plate 2i of the housing 20.

The motor I! has a wheel-like valve similar,

to the pump valve. The motor valve is positioned in a cylindrical valve chamber I and consists of an annular rim I2I. an annular hub I22 and a plurality of intermediate spokes I23. The annular hub I22 is rotatably mounted on an eccentric I24 (Figs. 1 and 1b) by means of a roller bearing I25, the "eccentric I24 being provided with an integral bushing I26 which is secured to the shaft III by means of a key I21 and is located between the bushing "I and a clamp nut I28 on the inner end of the shaft I00. As illustrated herein, the cylinder ports for the motor cylinders are indicated at I30 (Fig. 1) and communicate with the inner ends of the cylinders I04 by means of connecting passages I3I. The cylinder ports I30 are arranged to be connected alternately with the outer portion of the valve chamber I 20 (to which the pump ports are connected) and the inner portion of the valve chamber (to which the pump ports 9| are connected). ,Thus, in the operation of the transmission, when thepump pprts 90 are the outlet ports of the pump, the motor shaft will be rotated in a forward direction (1. e. the same direction as the pump shaft 45 is rotating) and the fluid exhausted from the motor will be returned directly to the pump ports 9| which are then pump inlet ports. If the wobbler for the pump is shifted in a counterclockwise direction from that shown in Fig. 1 beyond a radial plane so as to reverse the flow of fluid through the pump, the pump ports 9| become the pump outlet ports with the result that the flow of fluid through the motor is reversed and the direction of rotation of the motor shaft I00 is reversed. The Pump ports 90 then become pump inlet ports andcarry back to the pump the fluid exhausted by the motor. The circuit from the pump to the motor is closed so that the fluid (preferably oil) flows directly from one device to the other, provision being made as hereinafter more fully set forth to supply make-up fluid to the circuit to replace any which leaks out.

Due to the angle of the motor wobble plate as the pistons I05 act thereon, a side thrust on each piston is set up tending to cause twisting and, hence, binding of the piston. To counteract this side thrust, each cylinder I04 is provided with diametrically opposite recesses I33 and. H4. As best seen in Fig. 12, these recesses are disposed on a diameter that is tangential to a circle through the centers of the cylinders. Each recess I33 is connected by a duct I35 with the valve chamber I 20, and each recess I34 is also connected by a duct I36 to the valve chamber I20 radiall inwardly of the duct I35. These ducts I35 and I36 are governed by the motor wheel valve to supply pressure fluid to the recesses I33 when the motor-is driven forward and to supply pressure fluid to the recess I34 when the motor is driven in reverse direction. In ad dition to counteracting this side thrust, this construction also serves to reduce the heat generated in the motor block.

During the operation of the transmission, there are times when the casing 25 rotates with the pump shaft 45 and motor shaft I00, at which time the flow of fluid in the pump-motor circuit is substantially stopped or locked and the transmission is in substantially a 1:1 ratio. When functioning to operate the motor shaft I00 at a reduced speed, however, the casing 25 is held against rotation by means of the brake band 40. This brake band, as illustrated in Figs. 1, 6 and '7, has lugs I40 (Fig. 6) secured to its opposite ends. These lugs are pivotally connected to bell crank levers III and I42 which are pivotally mounted in a box I43 bolted on the rear side of the housing 20. Lever III is pivotally mounted on a pin I44 and is pivoted to one lug I40 by means of a pin I45. Lever I42 is pivotally mounted on a pin I40 and is connected to the other lug I40 by means of a pin I4'I. As illustrated in Fig. 6, one arm of the lever I4! is provide-:1 with gear teeth I48 which mesh with corresponding gear teeth I 49 on the lever I42. The levers are arranged to be actuated by means of an arm p is, forward," neutral and reverse.

more fully described. When the piston I53 is in the position shown in Fig. 6, the brake band 40 is engaged with the casing 25. When the piston I55 is moved toward the left, the brake band is released from the casing 25 and expanded and held centered against lugs 355 on the housing 25.

The pivot pins I44 and I45 for the bell crank levers HI and I42 are not anchored directly in the box I43, but are carried on a pair of laterall spaced and vertically extending bars I55 which are positioned within the box I43 so as to have a limited Vertical movement between an upper stop surface I55 and a lower stop surface I5I. This movable support for the bell crank levers is provided so that the casing 25 may have a slight rotary movement with respect to the housing 20 even when the brake band 40 is applied. The purpose for this arrangement will appear more fully hereinafter.

In Figs. to 18, there is illustrated a slightly modified form of brake actuating structure em-e ploying a pair of pistons I53 instead of a single piston. The pistons I53 are reciprocable in a common cylinder I54 having a port opening to each end and a port opening to the middle. With a pair of pistons I53, the bell crank lever I4I as well as the lever I42 has an arm I50 terminating in a spherical surface I5I'. The arms I50 extend at right angles to the arms bearing the teeth, and each engages one of the pistons I53. Movement of each piston I53 is limited by a fixed stop I58. In other respects the construction is the same as that of Figs. 1 to 11.

In the forms illustratedherein, the invention is adapted particularly for use in automotive vehicles and the controls are selected for such applications. Herein the controls are such as to make the operation of the transmission automatic, save where manual selection is desirable, and are hydraulic in character. Generally the controls include (see Figs. 11 and 15 to 18) a manually operable direction selector valve VM, an accelerator operated valve VA," a brake applying valve VBA, a brake release valve VBR, a valve VP for controlling the pressure of the fluid supplied by a makeup pump MP for control purposes, a pressure reducing valve VR in the makeup fluid supply line, and speed responsive valves VS and VS responsive to the speed of the drive shaft 45 and exercising control over the speed of the driven shaft I00 with respect to the speed of the drive shaft 45. Herein the direction selector valve VM has three operative positions, that celerator operated valve VA has two operative positions. One of these is shown in the position of the accelerator pedal AP in Fig. 15, in which the pedal is spaced from the accelerator proper represented at A. This position of the accelerator valve and of the accelerator pedal will hereinafter be referred to as the pre-idle position, inasmuch as it is a position to which the accelerator peda'l withdraws after. the accelerator proper has returned to its normal engine idle position. The second position of the accelerator valve VA in reality covers a range of positions defined by the range of operation of the accelerator A. One such position is shown inFig. 11 and the range extends from a point Just prior to engagement of the accelerator pedal with the accelerator A to a maximum actuation of the accelerator A. The brake applying valve VBA has two operative positions, one shown in Fig. 11, which is occupied when the reaction torque on the casing 25 is in a counterclockwise direction and the brake parts I55 have moved downwardly against the stop I51, and another shown in Fig. 17 in which the torque on the casing 25 has reversed, that is, in a clockwise direction and the brake parts I55 have moved upwardly against the stop I55. The brake release valve VBR likewise has two positions, namely, the brake applied position shown I in Fig. 11, and the brake released position shown in Fig. 17. The above mentioned valves, as well as the pressure control valve VP, the pressure reducing valve VR, and the speed responsive valves VS and VS will all be described more fully hereinafter.

As mentioned hereinbefore, a make-up pump MP is provided for supplying leakage fluid to the pump-motor circuit and also-for providing fluid under pressure to the control circuits of the transmission. Such a make-up pump may be of the type disclosed in my prior Patent No. 2,132,- 813, dated October 11, 1938. This pump consists of a toothed rotor I5! keyed to the shaft 45 and a corresponding internally toothed ring I62 meshing therewith. The ring I52 is eccentrio with respect to the shaft 45 so that a crescent guard I53 may project between the separated portions of the rotor and ring.

The rotor and ring of the pump are mounted in a recess formed in the inner face of a plate I 55 positioned in the outer end of the bore 24 of the housing 20, the recess being closed to complete the pump chamber by a flange 45' formed on the outer end of the sleeve bearing 45. As best seen in Fig. 6, the pump has an intake port I51 and a discharge or outlet port I59. The pump is effective to draw fluid from a tank I54 through an intake conduit diagrammatically shown in Fig. 11 at I55. Actually this conduit is composed of a tube or pipe I650 and a passage I55b formed in the housing 20 (see Fig. 1). Fluid discharged The acis maintained at a constant pressure by the pressure valve VP and is supplied to the valves for controlling the brake 40; to the leakage make-up valves; and through the manual valve VM and under the control of the speed responsive valves V8 and VS to the means for determining the position of the pump wobble plate.

In the form illustrated in Figs. 1 to 12, the automatic control for adjusting the output of the pump P includes, as previously stated, the speed responsive valves V8 and V8. The valve VS has a valve core I 01' the cylinder type slidably mounted in a radial bore I ll in the member 48, and the valve VS similarly has a valve core I82 of the cylinder type slidably mounted in a radial bore I83 positioned diametrically opposite to the bore I8I in the member 48. The valve core I55 is urged toward its innermost position by means or a coiled spring I54 positioned between the outer end of the valve core and a cap Ill screw threaded into a bracket I55a on the member 45. The valve I52 is urged toward its innermost position by means of a coiled spring I55 positioned between the outer end of the valve and a cap I51 screw threaded into a bracket Illa on the member 45. In general, the valve V8 acts as a pressure reducing valve for the fluid which flows from the make-up pump MP to the opposite ends of the shiftable cylinder 55, while the 'ed passage 293.

"valve vs' operates to control fluid for pre-loaih ing the valve vs. a v

As illustrated most clearly in the circuit diagram of Fig. 11,-fluid from the make-up pump MP is supplied to the cylinder 98 through means including a conduit I99 which communicates at its right hand or terminal end with the left hand end of cylinder 88, and at its left hand end com.- municates with an external annular groove I9! (Fig. 8) formed in the shaft 49. Physically the conduit I99, as best seen in Figs. 3 and 5, is made up of an oblique bore I 9911, a longitudinally extending groove I99b opening through the surface of the shaft 49, and oblique bore I990, an annular passage I99d, and a generally radial bore I99e opening to the left end of the cylinder 88 through the piston 89. A-branch duct I92 leads from-the conduit I99 (in the actual embodiment from the groove I99b) to the valve bore I 8!. Fluid is supplied to the right hand end of the. cylinder 88 through means including a conduit I93 having its-right hand or terminal end opening to the right end of the cylinder 88 and having its left hand end communicating with an annular groove I94 formed in the outer surface of the shaft 9-5. In its actual physical embodiment, the conduit I93 is composed of a bore I99a, a longitudinally extending groove I99b opening outwardly of the shaft 45, a generally radial bore l99c, an axial bore I99d, and a radial bore I98e-opening to the right hand end of the cylinder 88. The bore I93d is formed bythe insertion-in an axial bore I95 in the shaft 45 of a tube I 98 closed at one end, the tube having a reduced portion to form with the bore I95 the annular passage I99d of conduit I99. A first branch duct I98 leads from the conduit I98 (in-the physical embodiment (see Fig.

from the groove I98b)- to an' annular groove I9'I formed in the valve bore I8I spaced radially inwardly with respect to the point of communication with the bore of the branch duct E99. A

second branch I98 leads from the conduit I 93 and communicates with the valve bore I83, this branch being composed of a groove I98a in the periphery of the shaft 99 and right angular bores I981) in the member 48. The valve bores I8] and I89 are interconnected by a passage I99 composed (see Fig. .5) of a bore I99a in the shaft and 'of bores I999 in the member 48, the passage communicating with the inner end of the bore I8i and with the bore I88 inwardly of the point of communication therewith of the branch I 98. The innerend of the bore I88 is through a passage 299 connected to the tank I99, through'a devious route. The passage 299 discharges to the casing 25 and the fluid so returned passes over the operating mechanisms such as the pump wobbler between the shiftable cylinder 89 and the bore 85 through the bearings 91, eccentrics 88 and I24, bearings I 92 and I93 over the motor Wobbler and between the shaft I99 and the sup porting member 89 into an end chamber 29! in the plate 2i, thence through a passage 292 in a With the shaft in rotating at idling speed, for example, 859 R. P. M., both the valve core I89 and the'core I82 are in their innermost posi-,

tions. The valve V8 is, however,'adiusted to move to its outer position with any increase in speed of rotation of the shaft '49 above its normal idling speed, reaching its fully shifted position at about 599 R. P. M. With such increase in speed, the valve core I89 also has a tendency to shift outwardly and is made sensitive to shaftspeed variations by pre-loading' through application of fluid under pressure to the inner end of the core I89, such fluid being under the control of the valve VS. With a shift of valve core I82 outwardly, the. pressure in the conduit I98 is communicated to the valve bore I 83 by means of the branch I98 and is further communicated from the valve bore I88. to the inner end of the valve bore I8I by the passage I99. The valve *ple, as that shown in Flg..11, wherein it may be assumed that the shaft is rotating above idling speed, for example 499 R. P. M. In this position, the inner land of thevalve core partially. closes communication with the passage I96 and thereby causes a reduction in the pressure of the fluid applied to the right hand end of the cylinder 99 through conduit I93, whereas the left hand end of cylinder 98 is subject to the full pressure of the fluid supplied by the make-up pump MP to the conduit I99.

This unbalance of pressures will cause a shift of the cylinder 98 to the left with a tilt of the Wobbler from its neutral position, it being understood, of course, that such tilt is resisted by the reaction of the pistons 53 tending to restore the Wobbler to neutral position. As the speed of shaft 45 increases and the valve I89 continues to move outwardly, pressure is further reduced to the right hand end of the cylinder 68 with the result that the cylinder-tends to shift further toward the left with respect to the piston 66 to pivot the Wobbler to increase the stroke of the pump pistons 53.

' Since the capacity of the motor M is equal to the capacity of the pump P, the shaft I99 of the rib of the member 2i and the housing 29, and

an aperture in the housing. Similarly, discharging to the tank from the bore IN is a restrictthe valve core I92 has a pair of lands suitably spaced so that in the innermost position of the valve core I89 both the branch duct I92 and the branch duct I99 have complete communication with the bore I8I, while in the innermost position of the valve core I82 branch I98 is closed and passage I99 is in communication with the passage 299.

Each the valve core 189 and -I99 as a unit.

motor will rotate at the same speed as the pump shaft when the pump displacement reaches its maximum. Under these conditions, the reaction torque of the motor on the casing 25 will be balanced by the forward torque of the pump on the casing, so that if thebrake 69 is released the casing 25 will rotate In further explanation of, the above, with the pump Wobbler adjusted as illustrated in Figs. 1 and 11; wherein it is shown at approximately one-half maximum pump stroke, the motor shaft I99 will operate at approximately one-half the speed of the pump'shaft 45. Under these conditions the torque output of the motor shaft I99 45 and similarly the reactive torque on the motor cylinder block is twice the torque applied to the pump shaft 45. Since the torque applied I to the pump cylinder block is equal to the torque applied to the pump shaft 45, there is a reactive torque on the casing 29 as a whole tending This outward shifting of the valve core I89 with a resultant increasing unbalance with the shafts 45 and.

ance is reached between the motor output torque I and the pump input torque, a balance is also reached between the motor reactive torque on the casing 25 .and the pump forward torque on the casing 25 with the result that further increase in the speed of the pump shaft 45 causes the pump torque to overcome the motor reactive torque and the casing 25 tends to rotate in a forward direction (the same as the shafts 45 and I00). In a practical embodiment of the invention, it has been found that with a horsepower load on the motor shaft I00 equal to the horsepower input on the pump shaft 45 and with the pump shaft 45 rotating at a speed of 1200 R. P. M., the pump and motor torque on the easing 25 were balanced when the motor shaft speed reached 1100 R. P. M. When the casing tends to rotate in a forward direction, control means is By providing the valve VS, it is possible to use I a relatively weak spring I84 for controlling the valve VS. This provides for a more gradual acceleration of the motor shaft I00 with respect to the pump shaft 45. If, however, it is desirable to obtain a more rapid acceleration of the motor shaft I00 under load, it is preferable to provide a heavier spring I04 for the valve I80. Under these circumstances, the valve VS may be dispensed with, as illustrated in the modified form of the invention shown in Figs. 13 to 18. Under these circumstances, it is also preferable to provide a modified form of valve V This valve is illustrated diagrammatically in Figs. 15 to 18 and is shownas actually constructed in Figs. 13 and 14. The valve comprises a valve core 205 slidably mounted in a cylindrical sleeve tion of the valve core 205, as shown in Figs. 13 and 14, land 2I0 closes port ill, and land 220 closes port 2I5, while land 2I0'is disposed substantially in the middle of the groove 2I1. The port M5 and the port 2I5 through passages MI and 222, respectively, discharge to the casing .25 and thus are the equivalent of a discharge to the tank or reservoir I54, the fluid finding its way back to the tank in generally the same manner described in connection with passage 200. Port 2 is connected to the conduit I00 by a branch duct I92. The inner end of the sleeve 205, however, instead of being connected to the conduit I03 through another valve, is connected directly thereto by a passage I90, this passage, as best seen in Fig. 14, being formed in the shaft 45 and communicating with the longitudinal groove I93b.

It is believed readily understood from Figs. Hand 14, and from the circuit diagrams, particularly Fig. 15, that when the shaft 45 is operating at idling speed the valve core 205 will be in its innermost position and thereby admit fluid to opposite ends of the cylinder 58 so as to maintain the same pressure in both ends of the cylinder, thus permitting the pump wobbler to remain in its neutral or no-stroke position. As the shaft speed'increases above idling, the weight device 201 moves outwardly, thus permitting the valve core 205 also to move outwardly progressively to.

assume the positions shown in Figs. 16 and 17, which illustrate the forward torque multiplying and direct drive positions respectively of the transmission. As the valve core 205 shifts outwardly, the land 2I0 will, of course,restrict communication with the inner end of the sleeve 205 and may even cut it off completely so as to vary the pressure of the fluid in opposite ends of the 206 extending radially in the member 48. The

outward movement of the valve core 205 is controlled by a weight device 201 and a pair of coiled springs 200. The coiled springs are positioned between extensions 200 on the weight device and a ring 2I0 carried on the periphery of the member 48 and secured thereto by means of pins 2| I. Preferably a plug 2I2 is screw threaded in the weight device and has a cylindrical head 2I3 which slides in a bore in the ring 2I0 to act as a guide. In this form of the invention, the springs 208 exert suillcient pressure to maintain the valve core 205 in its innermost position illus.-. trated in Figs. 13 and 14 when theshaft is operating at idling speed. As the shaft speed increases, the weight device 201 moves outward- 1y. thus permitting the valve core 205 also to move outwardly.

The sleeve 206 of the valve V has opening therethrough a large port 2I4, a restricted port 2I5 and a port :li, and'formed internally thereof an annular groove 2I1 intermediate the ports 2 and 2I5. The valve core 205 has a land 2I0, a narrower land 2I0 closely adjacent the land 2I0, and a wide land 220. The land 2I8, as best seen in Fig. 14, has longitudinal passages 2I0 running therethrough. In the innermost posicylinder 58 to cause shift thereof in a direction increasing the angle of the pump wobbler.

Having described the valves VS and VS, the modified form of valve VS" and the fluid conduits or passages controlled by or associated with those valves, the circuit for supplying fluid under pressure will now be described. Inasmuch as the make-up pump MP is driven from the shaft 45 and thus would vary the pressure of the fluid discharged with the speed of rotation of the shaft, the pressure control valve VP is provided. This valve comprises a casing 225 having a valve seat 225 with which cooperates a valve 221. urged to seated position by a compression spring 228.

Opening to the casing to one side of the valve seat 225 is a passage 22! communicating at the other end with the pump discharge port I58,

. while opening to the casing on the opposite side Commumcating at one end with the passage m is a conduit in forming part of the circuit The valve core has 'a reduced portion 228 of'such length that when the valve core is in its intermediate or neutral position both of the grooves 236 and 236 are spanned by the reducedportion, Bhift of the valve core to the left to the position shown in Fig. 11 will, of course, cut oil the groove 236 and, likewise, shift of the valve core to the right to a corresponding extent. namely, tothe reverse position shown in Fig. 18; will cut on the groove 235. The core 234 is limited in its one end with the groove 252 therein, and at the other end with a passage 2636 formed in ,the closure 26, the conduit being completed by similar passages formed in each of the segmental portions 21, 26and 28 going tomake up the casing 25 and,- ofcourse, registering with one another.

movements by a pin 244' acting in a groove 234" I (see Fig. 10).

The conduit 2:: is connectedto the port 231,

while connected to communicate with the groove 235 is a conduit 239 formed in part in the mem-- ber 46 and opening through the member to communicate with the annular groove l9i-formed in the shaft 45 and with which the conduit I90 is .in communication. Similarly, there is in communication with the groove236 a conduit 24!! municating with the outerannular groove 494 on the shaft 45 which is in communication with the conduit I93. In the actual construction oi the manual valve VM, as shown in Figs. 6, 10 and lilo, there is shown a port 249 intended to be connected to tank and a port 252 through which The valve VR functions to maintain the presv sure in conduit at a constant value determined by the spring 244 regardless of changes of the pressure of the fluid supplied to the valve VR through conduit 250.' As' indicated, the upper end of the valve core 248' is subject to the pressure of the fluid in conduct 25!, a branch of which connects .with the upper groove 241.

If the pressure in conduit 25E drops below the value for which the valve VB is designed to '20 again partly formed in the'member 46 and comleakage fluid is returned to thetank, and the .valve is mounted in the same housing with the accelerator valve VA.

The pump MP also supplies fluid to make up the loss inthe main pump and motor circuit. In order that such make-up fluid may always be supplied before the actuating means for the wobbler i supplied, there is interposed in such make-up fluid supply circuit the reducing valve VR. This also serves to maintain the pressure of the make-up fluid constant, while the pressure of the control fluidmay be varied by adjustment of the pressure valve VP. The reducing valve VR comprises a casing 244 (formed by end wall 23) having a bore 244 with three longitudinally spaced internal annular grooves 245, 245 and 2 31. Reciprocable within the casing is a valve core 248 having lands at opposite ends of the-valve operate, then spring 244 raises the valve sufilciently to permit fluid to flow from conduit 250 through groove 245, along the reduced portion of the valve 248 and through groove 246 to the lower end of conduit 26l, thus raising the pres- 1 248. Thus when the transmission is again placed in operation, make-up fluid is immediately supplied to conduit 25! through valve VR, and since the valve VB is generally set at apressure lowerthan the settingof valve' VP, the make-up circuit is up to its full pressure before the control circult i up to its full pressure.

The fluid supplied by the make-up pump MP also actuates the brake actuating means, such fluid being under the control of the brake apply core. A compression spring 249 urges the valve core toward the groove 24'! in which position the portion of the valve core between the lands bridges the grooves 245- and 245, while in the posi-' tion shown in Fig. 11 the groove :46 is c1osed.

Fluid at the pressure maintained by the valve VP is supplied to the groove 248 through a conduit 256, in the actual construction taking the form of a passage communicating directly with the passage 225. Fluid under reduced pressure is discharged from the valve casing through a conduit 25l which, as best-seen inthe diagrammatic views, Figs. 11 and 15 to 18, terminates at one end in branches communicating with the grooves 246 and 24?, and communicating at the other end with an annular groove 252 formed internally of the member 3 i. In the actual physical construction, the conduit 25i takes the form of bores 25la formed in the. sleeve 46 and the closure member l68.. From the groove 252 .a

ing valve' VBA, the brake release valve VBR and the accelerator pedal actuated valve VA. The valve means VBA includes a valve core 268 mounted in a valve casing 265 forming part of the box 1153 and connected to a friction shoe 262 by means of a link 265. The friction shoe conduit 253 leads to the motor block '29 where it discharges through a. strainer 254 and thence through a pair of branch passages through check valves 255 to the motor valve chamber at a point outwardly of the rim l2! of the valve and also at a point inwardly of the rim I2l. Inasmuch as the casing 25 rotates at times, the conduit 253 in actual construction is composed of a passage 253a in the member 3| communicating at is in constant engagement with the cylindrical periphery of the motor cylinder block 29 and is held in such frictionalengagement by means of a coiled spring264. The casing 25 is enabled'to rotate sufilciently to actuate the valve core 260 because of the support of the bell crank levers ME and M2 on the slidably mounted bars I55, as previously described.

The casing 25E has a bore 256 and three longitudinally spaced annular grooves 261, 268 and 265. The core 266 has reduced portions 2716 and 219 so that in the position'illustrated in Fig. 11 the grooves 268 and 269 are bridged, while when the core is shifted to the right to the position shown in Fig. 15 the grooves 2st and 268 are bridged.

The brake release valve VBR has a casing 275 also formed as a part of the box M3; Extending longitudinally of the casing is a bore H5 in which is reciprocable a valve core 2' of the cylinder type which is constantly urged in one direction by a compression spring 218. The bore has an annular internal groove 21s at the end opposite the spring 218 and intermediate its ends three longitudinally spaced grooves 280, 26! and 282. The valve 'core 211 has a reduced portion 283 so positioned and proportioned that it bridges the grooves "I and 282 in one position while blocking the groove 288, while in anotherposition it bridges thegrooves 288 and 28! blocking groove 282. A port 284 opening to the groove 219 is never blocked but is at all times free to supply fluid to the end of the bore for acting on the end of the valve core counter to the action of the spring 218. A pin 285 limits the shift of the core 211 under the influence of fluid pressure supplied through port 284.

The accelerator pedal actuated valve VA, as previously stated, is enclosed in the same housing with the manual valve VM and is formed by a second bore 28'! in the casing 233. One end of the bore (see Fig. 10) is in communication with the adjacent end of the bore of the manual valve,

to be in communication with tank through the port 24!. Reciprocable in the other end of the bore is a valve core 288 connected by a link 289 to the accelerator pedal AP. The bore 281has two longitudinally spaced annular grooves 298 and NI, while the valvecore 288 has a reduced portion of considerable length so as to bridge the grooves 298 and 29l through the full range of operation of the accelerator A, such range being considered one position. The valve core.288 has an additional position, namely, the one which it assumes when the accelerator pedal moves to its pre-idle position, shown in Fig. 15, in which position the groove 298 is blocked while the groove 29! is in communicationwith the tank.

The various valve means just described are connected in, circuit as follows: A conduit 295' communicates at one end with the passage 229 and communicates at the other end with the groove 289 of the valve VBA. Fluid may also be supplied to the brake applying valve through a conduit 291 which communicates at one end with the conduit 248 and at the other end with the groove 281. The remaining groove 268 of the brake applying valve is connected by a conduit 293 to the groove 298 of the valve VA. A conduit 299 communicates at one end with the groove 29l of the valve VA and at its other end forks with one branch 388 communicating with the port 284 and the other branch 38l discharging to one end of the cylinder I54. A branch 382 of the conduit 29.":v communicates with the groove 288 of the brake release valve. The groove 28l of that valve is by a conduit 383 connected to the remaining end of the cylinder I 54 and groove 282 is by condut 384 connected to the tank. The conduits just described are in whole or in part formed by passages in the housing 28 (partially shown in Figs. 6 to 8) and completed by pipes not shown except in the diagrammatic views.

The circuit for the modified form of brake actuating means is the same from a functional standpoint as that Just described, and is even substantially the same from a physical standtacts the wobbler.

a feature of this invention, as well as the imviews showing the point of contact of the pistons with the wobbler, respectively, with the wobbler in'its maximum stroke position, and in a very small stroke position, that is, making about a 6' angle with the normal to shaft 48. In the discussion to follow, as well as wherever used in the claims, upper half" of the wobbler refers to the upper half as viewed in P18. 19, that is, the half of the wobbler which extends forwardly of its pivot. point with respect to the pistons, and is thus that half on which the reaction of the pistons is effective to return the'wobbler to its neutral or zero position. Likewise, lower half" will refer to thehalf of the wobbler below its pivot point and rearwardly of its pivot point as viewed inFig. 19. Wobbler arm will be employed to refer to the distance above or below the pivot for the wobbler at which a piston con- Force differential is the difference in effectiveness due to the longer wobbler arm" or moment arm, of the pistons acting on the "upper half" of the wobbler over those acting on the lower half."

It is inherent in wobbler type pumpstructures that the reaction of the pistons tends to return the wobbler to neutral or zero position, this being due to the increased length of the wobbler arm of the pistons acting on the upper half of the wobbler with respect to those acting on the lower half. This relatively large force acting to return the wobbler to neutral position varies with the angular position of the wobbler and also with the construction of the wobbler and the pistons.

Herein the wobbler and the pistons are so de- I signed that the force diiferential acting to return the wobbler to neutral position is so graduated for the different angular positions of the wobbler that in conjunction with the design of the remainder of the transmission the total force acting on the wobbler is substantially equal at all times. To that end, the ends of the pistons 83 are, as best seen in Fig. 19, rounded, while the surface of the wobbler contacted by the ends of the pistons 58, that is, the surface 89 of the outer ring 56, is also given a convex curvature in radial section.

point. With the modified form of brake actuating means, the branch 38I' of the conduit 299, instead of going to one end of the cylinder, discharges to the middle of the cylinder I54, and conduit 383 forks to provide branches 303' and 383" communicating with the ends of the cylinder I54. Because of this exact functional similarity and the great physical similarity, the same reference characters have been employed in both Fig. 11 and Figs. 15 to 18, except where there was an actual departure, in which case, whenever possible, the same character plus a prime was employed to show the relationship. The figures have also been referred to regardless of the form In a device such as disclosed'herein, it has been found to take approximately 3500 pounds per square inch pump output pressure to accelerate satisfactorily under load, whereas, to operate in a 1:1 ratio at full load requires approximately 1000 pounds per square inch pump output pressure. In other words, the per square inch pump pressure for starting is about three and one-half times the pump pressure required to operate at a 1:1 ratio under load, In view thereof, the surface 59 of the wobbler is given a convex curvature so that the force differential tons having the points of contact with the wobbler illustrated in Figs. 20 and 21, these figures, as previously mentioned, representing the position of the wobbler at 24 and 6 respectively. It will be seen from reference to Fig. 21 that the wobbler arms Wa, W1), W and Wd for th'e'pistons 53a to 53d, respectively, acting on the upper half of the wobbler are longer than the wobbler arms Wa to Wd', respectively, of the correspondingly positioned pistons 53a to 53d acting on the lower half of the Wobbler. The net effect, the difference in the length of the wobbler arms varying somewhat between different pairs of pistons, is that the effectivenes of the pistons acting on the upper half of the wobbler at a 6 angle is about 7% greater than that of the pistons acting on the lower half of the wobbler. Reference to Fig. 20 will disclose that the differences in the lengths of the wobbler arms Wa to Wd over the wobbler arms Wa to Wd are greater, with the net result such that the effectiveness of the pistons acting on the upper half of the wobbler is approximately 25% greater than that of the pistons acting on the lower half. It will thus be seen that the force differential with the wobbler at 24 is about three and one-half times that when the wobbler is at 6: It is to be understood, of course, that this same relationship holds true for all angular positions of the wobbler, giving a substantially straight line relationship.

It is believed readily seen, therefore, that with the pump output pressure at a 1:1 ratio of the transmission, two-sevenths of the pump output pressure at starting, 1. e., with the wobbler at 6, and with the force differential when the transmission is operating at a 1:1 ratio, that is, with the wobbler at 24, three and one-half times that at 6", the total resultant pressure on the wobbler will be the same for both conditions of operation. Since the pump pressure varies substantially uniformly from 3506 pounds to 1000 pounds as the pump goes from minimum to maximum displacement and since, as previously stated, the force differential varies substantially directly as the angular position of the wobbler increases, the total resultant pressure on the wobbler will be substantially the same throughout theentire range of operation of the transmission. This uniformity of total pressure permits the use of small diameter pistons and above all permits accurate and proper control of the transmission under the constant pressure supplied to the cylinder 68.

Having described the construction of the transmission and its control means, the operation thereof will now be described briefly to render the invention more readily appreciated by a correlated statement of the functions of the various parts. In describing th operation, reference will primarily be made to the circuit diagrams of Figs. to 18, showing the modified construction. Let it be assumed that the pump shaft 45 is rotating at idling speed in a clockwise direction, as viewed from the left in those figures, and that the manual valve VM is in its neutral position. Under those circumstances, the various valves and fluid actuated control devices will be in the positions shown in Fig. 15. More particularly, with the manual valve VM in its neutral position. control fluid is supplied to both grooves 235 and 236 and thus is supplied to both ends of the cylinder 68 at the same pressure. The cylinder 68 will therefore place the pump wobbler in its no-stroke position, with the result that though the pump is being driven no fluid is being discharged to the motor M. The fluid pressure in the cylinders of both the pump and the motor, as well as in the passages of the valve structure, is that of the make-up fluid determined by the adjustment of the pressure reducing valve VR. The speed responsive valve VS" is not actuated and thus is in its innermost position and would in any event have no influence so long as the manual valve is in its neutral position. The accelerator valve VA now connects the conduit 299 with the tank or reservoir, thereby relieving the pressure between the pistons I53 of the brake actuating device, as well as the pressure tending to shift the core of the brake release valve VBR. Under those circumstances, the brake band 40.is released.

To condition the transmission for forward drive, the manual valve VM is shifted to its forward position shown in Fig. 16. In that position, groove 236 no longer receives control fluid from the make-u pump and only groove 235 receives such control fluid. The pressure of the control fluid is thus transmitted through the conduits 239 and I99 to the left hand end of the cylinder 68. This same full control pressure is also transmitted to the right hand end of cylinder 68 through the branch duct I92, valve V past land 2I9 and passages 2I8' in land 2l8 (see Fig. 16a), conduit I99, and conduit I93, the valve VS" while in its inner position not functioning to reduce the pressure. Thus the cylinder 68 and hence the wobbler of the pump remain in no-stroke position, even though the manual valve has been shifted to forward position, until the operator accelerates the speed of rotation of the shaft 45.

As the accelerator pedal AP is depressed, it first shifts the core of the accelerator valve VA to the position shown in Fig. 16 before it engages and actuates the accelerator A. By such shift of the accelerator valve, the circuit is conditioned to apply the brake 40 as the transmission begins to operate, and the casing 25 tends to rotate under the counter torque, thereby shifting valve VBA, such application of the brake occurring in the following manner: Control fluid from the make-up pump flows through conduit 295, the brake applying valve VBA (grooves 269 and 268 now being bridged), conduit 298, the accelerator valve (grooves 290 and 29I now being bridged), conduit 299 and its branches 300 and 31, respectively, to the end of the bore in the brake release valve VBR and to the midpoint of the cylinder I54. Valve core 211 is shifted to the position shown in Fig. 16, thereby blocking groove 28!) and bridging grooves 28I and 282 serving to connect the ends of the cylinder I54 to the tank, and thus enabling the pressure between the pistons I53' to separate the pistons and apply the brake band 49.

With further depression of the accelerator pedal, the speed of rotation of the shaft 45 is increased and, as a result the speed responsive valve VS" shifts outwardly under the influence -of centrifugal force and the pressure of the fluid from passage I99 (Figs. 16 and 16a) acting on the inner end of the valve core 295. With the initial outward shift, (see Fig. 16a) the land 2I9 of the valve corerestricts the communication between conduits I and I93 through the valve VS" and at the same time the restricted port H5 is opened, resulting in a differential in pressure in the opposite ends of the cylinder 68. As the land 2I9 moves increasingly ofl center with respect to the groove 2", it increasingly acts to reducethe pressure of the fluid flowing to the end of the valve bore. Thus, the pressure of the fluid flowing to conduit I93 is decreased and also the tendency to shift the valve outwardly diminishes until the valve is completely under the control of centrifugal force. This force alone is never suflicient to shift the valve to the limit of its outward movement. In Figs. 16 and 16a, the valve core is, for exemplary purposes, shown in an intermediate position where it just cracks the passage through the valve. The left hand end of the cylinder now will be at the full con- 1 trol pressure while the right hand and will be at a reduced pressure, resulting in a shift of the cylinder 68 to the left to the position shown in Fig. 16. The pump will now discharge fluid to the motor M tending thereby to drive the motor M and at the same time setting up a reaction torque in the casing 25. This reaction torque is in the direction indicated by the arrow in Fig. 16 and thus through the shoe 262, and the limited movement of the bell crank levers shifts the brake applying valve VBA to the left to the position shown in Fig. 16, thereby making possible the application of the brake previously described. With the casing 25 now held against rotation, the shaft I of the motor will be driven, the torque of the shaft 45, of course, being multiplied. pump wobbler will, of course, be dependent upon the pressure differential in the cylinder 68, which is a function of the speed of rotation of shaft 45 and upon the load on the transmission, since the reaction of the pistons, as previously more fully described, is such as to return the wobbler to its no-stroke position. The transmission will thus automatically adopt that adjustment which will enable it to carry the load.

As the core of the speed responsive valve VS" continues to shift outwardly under increased speeds of the shaft 45, it completely prevents communication between the conduits I90 and I93 (this occurring at about 1200 R. P. M.), thereby producing a still greater pressure differential in the opposite ends of the cylinder 68. This position of the valve VS" is shown in Figs. 17' and 17a, and the result is that the left hand end of the cylinder 68 is under the full pressure of the control fluid while the right hand end is at no pressure, being connected with the tank through the port 2I5. The cylinder 68 thus tends to shift to its extreme left position, shown in Fig. 1'7, which is the maximum stroke position of the pump wobbler. This position, of course, is also dependent upon the load on the transmission. As the torque on the shaft 45 required to drive the load decreases, the reaction of the pistons 53 on the wobbler decreases, permitting increased tilt of the wobbler until maximum stroke of the pistons 53 is obtained. As the displacement of the pump increases, the speed of rotation of the motor increases and the torque of the motor shaft decreases relatively to the torque applied to the pump shaft until the motor torque is equal to the applied torque. When this balance is reached, the reaction torque on the casing 25 produced by the pump equals that'produced by the motor and further increase in the speed of the pump shaft would cause the pump torque to overcome the motor reactive torque, with the result that the casing 25 now tends to rotate with the shafts, which is in the direction indicated by the arrow in Fig. 17.

The tendency of the casing 25 to rotate in t e The exact position of the' same direction with the shafts 45 and I00 is permitted, first, by the play provided for in the mounting of the bell crank levers HI and I42. This initial rotation shifts the core of the brake applying valve VBA to the right to the position shown in Fig. 1'1. In this position, 'the grooves 261 and 268 are bridged, thereby relieving the pressure between the pistons I53 and in the end of the bore 216 of the brake release valve VBR. The connection to tank is effected through the conduit 299, valve VA, conduit 298, valve VBA, conduit 291, conduit 240, a part of conduit I93, conduit I99, port 2I5 of the valve VS, and passage 22 I. Relief of the pressure in the end of the bore of the brake release valve VBR permits the spring 210 to shift the valve core to the position shown in Fig. 1'7, in which position the grooves 260 and 28I are bridged. As'a consequence, fluid from the make-up pump flows through the con'duit 295, conduit 302, valve VBR, conduit 303, and its branches 303 and 303" to the ends of the cylinder I54. This releases the brake, permitting the casing 25 to rotate with the pump and motor, with the result that the transmission is locked to operate substantially as a unit in a 1:1 ratio. During operation under these circumstances, there is substantially no flow of fluid from the pump to the motor or vice versa, the force being transmitted through substantially static columns of fluid.

If it is desired to place the transmission in reverse, the manual valve MV is shifted to its reverse position shown in Fig. 18. In this position, the groove 235 is blocked and control fluid is supplied only to the groove 236. Full control fluid pressure is now applied to the right hand end of the cylinder 68, being transmitted through the conduit 240 and the conduit I93. This pressure is, through the conduit I99, (see Fig. 18a) also applied to the inner end of the core 205 of the valve V This pressure added to the centrifugal force moves the valve core outwardly beyond its direct drive position to open port 2 I6 which leads to the tank. The leftvhand end of cylinder 68 is thus through the conduit I and branch duct I92 and valve VS" connected to the tank permitting the cylinder 60 to be shifted to the limit of its position to the right. This reverses the tilt of the wobble plate, thereby causing the pump to operate the motor in reverse direction. Under these conditions, the reaction torque is in the direction indicated by the arrow in Fig. 18, and consequently the core of .the brake applying valve is shifted to its right position, shown in Fig. 18. The brake release valve VBR is now shifted and pressure fluid is supplied between the pistons I53' to apply the brake, the same as previously described in connection with the operation of the transmission in forward torque multiplying condition. The control fluid is, under these circumstances, derived through the conduit 291, conduit 240, the manual valve, and conduit 232. The fact that the right hand end of cylinder 68 is connected to tank through port 2I5 has no influence because the port is so restricted.

I claim as my invention: I

1. A hydraulic transmission comprising, in combination, a, driving element, a driven element, a variable displacement pump coupled to said driving element including means responsive to an increase in torque in the transmission tending to decrease pump displacement, a motor coupled to said driven element and connected in hy- 

